I'm having trouble understanding axis locking methods, specifically in regards to local coordinate systems. I have three questions about this topic.
In most explanatory threads on the internet its explained that, if you use any manipulation tool (i.e., move, scale, rotate, etc) and you use axis locking by pressing either x, y or z, the first time you press it will lock to the regarding global axis. You press the second time and it will perform the manipulative action you chose along a local coordinate system. This is also explained in the blender manual:
...yeah well, it doesn't do that in my case. To figure out what's happening, I created a random object and tried extruding a face. When I extrude a face, it generally starts by scaling along some local Z axis:
When I press z for the first time, it extrudes along the global z axis. So far as explained. But when I press a second time, it doesn't extrude in the local direction again, but it releases it.
Now ok, I can see that, when faces are extruded, its kinda more intuitive if the first suggestion for the direction to extrude in is in the direction of the normal vector. This leads me to conclude that, with any selection (no matter if verticies, edges or faces) the local coordinate system is arranged in such a way that the average normal vector is considered the Z-axis.
First question to you: Is that assumption correct?
Second question to you: When I select a face on my random object (such as the one in the image above), I would like to see the local coordinate system, so that I get an idea where my manipulations are headed when I lock to a local axis. However, I never really get to see the local coordinate system. So, I have an idea where Z lies (by estimating the average normal vector of my selection), but I never really know where X and Y are going before I do anything. Is there any way to display a local coordinate system of a selection? How does blender determine how X and Y are oriented locally in the first place? Btw, if I choose "local" in the transformation orientation menu, no local coordinate system shows up either.
Third question to you: Is there maybe a possibility to create a custom coordinate system which I can use to manipulate my selections? So that, for instance, I can customize where my Z-axis is oriented and lock to it?
Thanks for your help in advance.